1. Technical Field
The present invention relates to a machine provided with a pulsating oil pressure reducing device for reducing the pulsating oil pressure in an oil passage, such as an internal combustion engine provided with an oil pump.
2. Description of the Related Art
In a positive-displacement oil pump, the volume of an enclose space is increased to suck an oil into the enclosed space and is decreased to discharge the oil from the enclosed space. Therefore, both oil pressure in the suction passage connected to the inlet port of the positive-displacement oil pump and oil pressure in the discharge passage connected to the outlet port of the positive-displacement oil pump pulsate. The pulsating oil pressure causes undesirable phenomena including vibration and noise generation. For example, the pulsating oil pressure vibrates an oil filter placed in the discharge passage and causes the oil filter to generate noise. The pulsating oil pressure in the suction passage propagated to the oil contained in an oil pan vibrates the oil pan and causes the oil pan to generate noise. A technique disclosed in, for example, JP-A 2005-146995 forms an oil chamber in a branch passage branched from an oil passage to reduce pulsating oil pressure.
Air leaks through small gaps into oil passages and the oil pump while the oil pump is not operating. Therefore, the oil contains a comparatively large amount of air at an initial stage of operation after the oil pump has been started. If the air contained in the oil accumulates excessively in the oil chamber, the pulsative pressure suppressing effect of the oil chamber is reduced. Excessive accumulation of air in the oil chamber can be avoided by connecting ports formed in upper parts of the oil chamber to the oil passage.
The ports formed in the upper parts of the oil chamber need to be opened into the oil passage to discharge air from the oil chamber into the oil passage. Such a requisite condition places restrictions on the position of the oil chamber relative to the oil passage and on the placement of the oil chamber and, consequently, the degree of freedom of placing the oil chamber decreases.
In a machine provided with oil passages, such as an internal combustion engine, the arrangement of the oil passages is dependent on the construction of the machine and the arrangement of an oil pump and an oil filter. If an oil passage and an oil chamber are arranged horizontally in side-by-side relation, it is difficult to discharge air efficiently through a discharge port formed in the upper part of the oil chamber into the oil passage.